Several processes, industries, and applications require a metallic surface to come into contact with a liquid. Water and other liquids, for instance, are often pumped through metallic pipes. Boats and other water vessels may have metallic hulls that contact water. Other industries, including but not limited to, petrochemical, power generation, food, and construction industries, also include liquid exposure to a metallic surface. Many, if not all, of these processes would benefit from liquid repellency at a metallic surface. For example, liquid repellency in pipes could enable more efficient fluid transport due to hydrodynamic drag reduction, which could lead to more effective drainage or cleaning of storage tanks, for instance. In other applications, such as power generation and desalination industries, enhanced heat transfer efficiency during drop-wise condensation of water vapor could save energy, and thus money. Liquid repellency could also improve the corrosive resistance of a metallic surface, thereby prolonging the lifetime of construction materials, as one example.
Previous efforts to fabricate water-repellant metallic surfaces include methods using laser ablation, surface coating, electrodeposition, electro-less deposition, and chemical etching. Surface roughness may be created with high fidelity and good mechanical stability by laser ablation techniques, but the process is difficult and scale up is costly. Surface roughness can also be created by application of a coating that has inherent roughness, such as one with embedded particles, but this method can generate intrinsic stress that can degrade both the mechanical stability of the surface and the interface between the metallic object and the coating. In such a method, adhesion of the particles and/or coating is also a concern. Electrodeposition or electro-less deposition methods to induce roughness on metallic surfaces also raise concerns about adhesion and mechanical stability at the interface between the deposited material(s) and the metallic object due to intrinsic and/or thermal stresses. Chemical etching methods often result in sharp features of the metallic surface, which may lack the necessary mechanical stability for wide applicability.
Therefore, there is a desire for a method to create a liquid-repellant metallic surface that is mechanically stable. Further, there is a desire for a method for anti-wetting a metallic surface that is scalable. Various embodiments of the present invention address these desires.